Three years ago today, Suicide Squad director David Ayer tweeted a photograph of actor Jared Leto portraying the supervillain Joker which subsequently spawned numerous parodies and copypastas.

Nine years ago today, nature photographer Casey Myers uploaded a photograph of a cheeky-looking horned lizard who later became a reaction image used in response to lowbrow humor.

Two years ago today, photographs of a young man performing gravity-defying stunts in a hallway made their way on to Twitter, subsequently spawning numerous image macros captioned with jokes referencing the game "the floor is lava."

Seven years ago today, the earliest known chart satirically depicting the life cycle of an internet meme reached the front page of the /r/funny subreddit.

What started in the 1970s as code for "getting stoned" evolved to become a cornerstone meme in stoner culture on the internet.